This present invention relates generally to improvements in rotational adjusting mechanisms, and particularly to an improved manual drive mechanism in a device equipped with a powered or automatic drive means, such as an electric motor.
Where it is desired to manually shift or advance a web which is shifted or advanced by an automatic or powered drive means, such as a motor, it has been customary to deactuate or stop the drive means, then disconnect the web being advanced from the drive means, and connect the web to a manual drive means, so that an operator may mannually shift or advance the web a desired distance.
To this end, it has been necessary to separately provide the manual drive means and the automatic drive means and to position the advanceable web connectably in a manner engageable with both the manual and automatic drive means.
Furthermore, the drive means requires the use of a means for transmitting the drive force thereof to the web being advanced, and a means for interrupting the transmission of such drive force thereto. In addition, a means for changing over between the automatic drive and the manual drive operations must be provided for the drive means. Thus, a great complexity in the construction of the drive apparatus per se, as well as a great difficulty in the handling thereof result.
In the event of an improper switching operation between the manual drive and the powered or automatic drive operations, the drive force of the powered drive means, such as an electric motor, would be transmitted by way of the manual drive means to an operator's hands, entailing a danger of injury or inconvenience to the operator.
Such a drive mechanism or device is employed in various mechanisms or machines, such as an automatic positioning or detecting mechanism for a microfilm handling machine, a moving picture compiling machine for a 8-mm film, an automatic machine tool, and so forth. Typical of these machines is a manually film-driving device for manually correcting the position of the projected image or a selected frame of a microfilm, for use in a microfilm automatic probing machine, wherein a microfilm is shifted by a powered drive means, such as a motor, so as to locate a selected frame properly at a projecting position.
In such a device, when it is desired to project an image of a selected frame of a microfilm in roll form onto a screen, a procedure must be followed in which the microfilm in roll form is advanced or shifted by energizing a motor; a mark on the desired frame of the film is optically detected; and immediately before the desired frame arrives at the projecting position, the motor is stopped, so as to locate the desired frame properly in the projecting position, so that an image of the desired frame is projected onto a screen. However, the projection magnification ratio of a microfilm is commonly as large as 20 times, and even only a small positional deviation of the selected frame from the projecting position is greatly enlarged on a screen. For this reason, accuracy in the control of the frame position is necessary. However, it is difficult to accurately start and stop the drive mechanism, such as a motor, as well as the mechanism for braking the drive mechanism, because of the inertia of the rotor and other factors, even if a pulse motor or a potentiometer is used. Thus, the overrunning of the selected frame from the proper projecting position results, leading to the excessive shifting of the projected image from the proper position on the screen, or in the extreme case the projected image completely passing the screen.
The correction of the positional deviation of an image projected on a screen has hitherto been accomplished by manually intermittently operating a drive means, such as a motor, or a decoupling or disengaging means, such as a clutch. However, because the operation of such means is instantaneous, it necessitates repeated corrections by a skilled operator to locate the desired frame in a proper position.
Where the correction of the position of a selected frame of a microfilm is made without utilizing such drive means, a microfilm must be shifted by a separate shifting means, after the film has been disengaged from such drive means. For this purpose there must be provided a mechanism for interrupting the connection between the drive means and the film and a manual film-drive means for the driving apparatus, resulting in a high complexity in the construction of the drive apparatus. Furthermore, a switching operation between the automatic drive mode and the manual drive mode is required, incurring the danger of injuring the operator due to an inadvertent transmission of the drive force from the automatic or powered drive means to the manual drive means, in the event of an improper switching operation.